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Sharp one-dimensional (1D) and two-dimensional (2D) structures are required for stable and efficient field emission. 1D metal oxide and 1D carbonaceous nanostructure material have been used widely for exciting field emission applications. On the other hand, planar, continuous 2D nanostructures have been less explored, as most often, they offer inefficient field emitters, having high turn-on field and low emission current density. A combination of 1D and 2D nanostructures is expected to improve field emission properties. In the present study, nickel oxide nanostructures were considered as 1D nanostructures, which were synthesized on cleaned, polished, nickel foil substrate by wet chemical treatment through the nano-seed mechanism. Pyramidal shape nanostructures of NiO were found onto nickel substrate. 1D nanostructure, NiO nanostructure, does not show any field emission response. Further, graphene oxide (GO) was used as the 2D nanostructure.) While nickel oxide nanostructure and graphene oxide individually demonstrated very low emission properties, hybrid of these materials show modified surface topography and enhanced field emission properties. The field emission response of graphene oxide on Ni foil shows 6.7 V/μm turn-on field and maximum current density of 28 µA/cm2, whereas graphene oxide on NiO nanostructure has enhanced field emission response. In the case of NiO–GO, the turn-on field and maximum current are 5 V/μm and 173 µA/cm2, respectively. Field emission properties are enhanced further with the reduction of the NiO–GO hybrid and depositing CNT of NiO. The maximum current density of 3.7 mA/cm2was observed for the NiO–CNT hybrid.

The interaction between the metallic substrate and precursor suspension in the electrophoretic deposition (EPD) plays a significant role to reduce graphene oxide (GO) from suspension. Possibility of manipulating this interaction to achieve desired functional properties has been studied in this work. From the Pourbaix diagrams for metals, it was identified that modifying pH of the precursor suspension would result in different situations at the interface of the anodically polarized metallic substrate and graphene oxide (GO) aqueous suspensions. Different values of pH ensure that the metal is either passivated or corroding with varying products, in different pH regions. Such a manipulation of the substrate–suspension interface resulted in significantly different characteristics of the deposited reduced graphene oxide (r-GO) film including morphology, structural characteristics and adhesion strength with the substrate. Also, field emission characteristics of the r-GO films deposited in different conditions were studied. The results showed a distinct possibility for optimizing the field emission properties simply through modifying pH of the suspension. The field emission characteristics of deposited (GO) films could be tailored with deposition parameters.

The present investigation is aimed to find a thread between various surface textures of polycrystalline Cu–Ni alloys, in cold-rolled and annealed conditions, and the nature of graphene, grown by th...

Graphene and its derivatives such as graphene oxide (GO) and reduced graphene oxide (rGO) are the potential candidates for high-performance field emission devices owing to their unique geometry and electrical properties. However, flat surface of GO and rGO results in lower field emission efficiency due to emission of electrons only from sharp edges of GO and rGO sheets. In the present study, GO and rGO layers were deposited on both CuO and Cu nanorods (NRs) to enable maximum field emission current density at low applied field via geometrical field enhancement. CuO NRs were synthesized on Cu foil using wet chemical method and Cu NRs were produced through chemical and thermal reduction of CuO NRs. GO layers were deposited on CuO and Cu NRs through dip coating method. GO was converted to rGO through thermal reduction. A comparative study of the field emission properties of CuO, GO@CuO, rGO@CuO, Cu_H 2, GO@Cu_H2, rGO@Cu_H2, Cu_NaBH4, GO@Cu_NaBH4, rGO@Cu_NaBH4 samples was performed. The basic idea behind deposition of GO and rGO sheets on CuO and Cu NRs was to create sharp protrusions in GO and rGO sheets to achieve enhanced field emission properties. Local field enhancement at the apex of sharp protrusions allows tunneling and hence emission of electrons from tips at considerable lower voltage. Highest current density and highest field enhancement factor were obtained in thermally reduced GO@CuO (i.e rGO@CuO) sample.

In the present age of industrialization, oil contamination in the waste water has become a huge global concern due to its several negative impacts on human health and aquatic ecosystem. In order to address this problem, a novel oleophobic and super-hydrophilic graphene-based membrane has been developed using simple and cost-effective vacuum filtration methodology. Prior developing the membranes, the graphene oxide (GO) sheets were crosslinked with tannic acid (TA) molecules in order to improve their mechanical and surface properties. To obtain the structural and morphological information of the membranes and their constituents, Field Emission Scanning Electron (FE-SEM) microscopy, X-Ray Diffraction (XRD), FTIR spectroscopy and Raman spectroscopy was used. When tested with simulated oilfield effluent samples, these membranes exhibited significant reduction in the values of chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS) and turbidity demonstrating low-oil adhesion and preferable oil rejection rates. Moreover, such crosslinked membranes are highly stable which can withstand the pressure of water filtration. In such a way, TA crosslinked GO membranes present a robust and efficient way to treat oil contaminated water released from various industries which can be reused for numerous further applications., Nanomaterials; Materials application; Materials chemistry; Materials synthesis; Environmental pollution; Graphene based materials; Water purification from oil contamination, Superhydrophobic material.

A two-step, low-temperature thermal chemical vapor deposition (CVD) process, which uses camphor for synthesizing continuous graphene layer on Cu substrate is reported. The growth process was performed at lower temperature (800 °C) using camphor as the source of carbon. A threezone CVD system was used for controlled heating of precursor, in order to obtain uniform graphene layer. As-grown samples were characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). The results show the presence of 4–5 layers of graphene. As-grown graphene transferred onto a glass substrate through a polymer-free wet-etching process, demonstrated transmittance ~91% in visible spectra. This process of synthesizing large area, 4–5 layer graphene at reduced temperature represents an energy-efficient method of producing graphene for possible applications in opto-electronic industry.

Field emission is a process of electron emission from the surface of a material through quantum tunneling in the presence of an applied electric field. Emission of electrons from a material becomes easy if material is synthesized in the form of nanoscale sharp tips. In the present work, we synthesized one dimensional nanostructures (1-D) such as copper oxide (CuO) nanorods and carbon nanotubes (CNTs) by wet chemical and chemical vapor deposition (CVD) methods, respectively. As the electron field emission (FE) from the flat surface of graphene is challenging, the reduced graphene oxide (RGO) was coated on CuO nanorods and CNTs to prepare RGO based hybrids for field emission. Basic idea to support RGO on 1-D nanostructures was to produce high density sharp protrusions/ridges in RGO sheets. A comparison between the FE characteristics of 1-D nanostructures and RGO based hybrid emitters was performed.

Ever since the more-than-decade-old discovery of application of mechanical exfoliation to obtain graphene, this 2-dimensional material was known for its soaring promise in various applications, owi...

Hexagonal boron nitride (BN) is structural analogues to graphitic structure of carbon. Similar to graphene and carbon nanotubes, BN also has nanosheets structure, also known as white graphene and nanotubes structure. These BN nanostructures show excellent properties, such as high stability, mechanical strength and resistant to chemicals. Synthesis of BN nanosheets is easier as compared to synthesis of its 1D nanostructure due its hexagonal layered structure, in which stacks are attached with each other by weak Van der Waals forces. In the present work, synthesis and applications of 1D and 2D nanostructures are discussed. Growth of BN nanotubes on tungsten substrate was performed by using copper as catalyst with a simple and easy method. Synthesis of fluorescent BN nanoflakes was performed using solid precursor, boric oxide and urea for boron and nitrogen, in a high-temperature furnace under argon atmosphere. The product was ultrasonicated in water to get completely stable dispersion of fluorescent nanoflakes as final product. Both The product was then characterized by FESEM, TEM, FTIR. The fluorescence behaviour of BN nanoflakes was also measure and applied for bioimaging of breast cancer cells (MCF-7).

In this study, soda lime glass was reported to use as transparent conducting electrode. Soda lime glass was made conducting with graphene film deposited through simple, low cost, scalable and easy to operate thin film deposition technique. Graphene oxide was dip-coated on soda lime glass, followed by reduction into rGO by thermal annealing in two different atmospheres Ar and Ar+H2 at 500 °C. Bonding strength of GO and rGO (Ar and Ar+H2 treated) with soda lime glass were measured through nanoscratch technique to understand the adhesion behavior of film with substrate. There was no significant effect of reduction atmosphere found on transmittance of the films. However, films, reduced in Ar+H2 atmosphere, showed the low sheet resistance than reduced in Ar only. Highest transmittance of 97.98% and lowest sheet resistance of 12.5×103 Ω/sq were calculated under different processing conditions.

Dissociative chemisorption of CH4/H2 gas mixture during graphene growth was investigated on commercially available Ni and Ni-33wt.% Cu substrates. Catalytic activity of both the substrates was severely decreased by employing very low gas pressure, thereby allowing the examination of very initial stages of dissociative-chemisorption. The chemisorption characteristics of the nickel rich nickel-copper alloy were interestingly found to be similar to those of pure copper, i.e., preferential adsorption of hydrogen over methane. These observations led to an in-depth understanding of the graphene growth mechanism on these substrates.

Reduced graphene oxide coated soda lime glass can act as an alternative transparent/conducting electrode for many opto-electronic applications. However, bonding between the deposited reduced graphene oxide film and the glass substrate is important for achieving better stability of the coating and an extended device lifetime. In the present study, delamination energy of reduced graphene oxide on soda lime glass was quantified by using nanoscratch technique. Graphene oxide was deposited on soda lime glass by dip coating technique and was thermally reduced at different temperatures (100 °C, 200 °C, 300 °C, 400 °C and 500 °C) and treatment time (2 h, 3 h, 4 h, 5 h and 10 h) in Ar (95%) with H 2 (5%) atmosphere. An inverse behavior of delamination energy with temperature and treatment time was observed, which could be correlated with the removal of oxygen functional groups. Sheet resistance of the film demonstrated a steady decay with increasing temperature and treatment time. Functional groups attached to the graphene planes have more influence on conductivity than groups attached to the edges. Removal of functional groups could also be related to optical transmittance of the samples. Knowledge generated in this study with respect to delamination energy, sheet resistance and optical transmittance could be extensively used for various opto-electronic applications.

In order to deal with the challenge of biofilms and its associated infections, it is important to develop some efficient methodology which prevents the formation of biofilms over the surfaces. Herein, we have successfully developed an antibacterial and antibiofilm composite using non-toxic and hydrophobic nanomaterial, graphene nanoplatelets, via facile two step methodology including functionalization and subsequent hydrothermal treatment. The as-prepared composites were characterized using FE-SEM, FTIR and Raman spectroscopy to obtain morphological, compositional and structural details. In addition, the antibacterial efficiency of these composites was investigated against antibiotic resistant S. aureus and E. coli. Afterwards, graphene composite based epoxy coatings were prepared on glass substrate and tested for their antibiofilm efficiency against methicillin resistant S. aureus strain. The abundant presence of hydroxyl groups over the surface due to tannic acid, hydrophobicity of graphene and epoxy and remarkable antibacterial efficiency of tannic acid (TA), silver (Ag) and graphene synergistically enhance the antibiofilm efficiency of such coatings. This work presents a new strategy to develop a multifunctional coating and subsequently lessen the risk of biofilm assisted infections.

In this report, few- and multilayer graphene was fabricated on different substrates by pulsed laser ablation of a highly ordered pyrolytic graphite target under optimized growth conditions, using a pulsed nanosecond Q-switched Nd:YAG laser at 355 nm (3.5 eV). The nondestructive micro-Raman spectroscopic study on our samples has revealed few- and multilayer graphene formation. The number of graphene layers was found to be reduced with the increase in growth temperature. At substrate temperature of 750 °C, the ratio of intensities (I 2D/I G) was calculated from the Raman spectra of the graphene samples to be 0.15 which confirms the multilayer graphene formation, while for graphene film grown at 800 °C, I 2D/I G ratio was 0.27 indicating formation of less than five layers of graphene or few-layer graphene. The thickness of few- and multilayer graphene was also confirmed using atomic force microscopy, whereas the microstructure of few- and multilayer graphene was investigated using scanning electron microscopy. The electrical properties in function of growth temperature were evaluated with two-point probe measurements. This work presents a simple, fast, and controllable alternative effective laser technique to synthesize few- or multilayer graphene.

Graphene nanoplatelets (GNP) reinforced aluminum matrix composites, with ≤5 wt% GNP content, were synthesized by spark plasma sintering (SPS). GNPs were found to withstand severe conditions of high pressure and temperature during processing. Strength of composite was observed to be depending on the content and uniform dispersion of GNP in aluminum matrix, as verified by scanning electron micrographs. X-ray diffraction analysis confirmed that no reaction products exist at Al-GNP interface in significant amount. Instrumented indentation studies revealed improvement in hardness by 21.4% with 1 wt% GNP. This is due to the presence of stronger reinforcement, which provides high resistance to matrix against deformation. Improvement in yield strength and tensile strength was 84.5% and 54.8%, respectively, with 1 wt% GNP reinforcement. Properties deteriorated at higher concentration due to agglomeration of GNP. Reinforcing effect of GNPs, in terms of strengthening of composite, is found to be dominated by Orowan strengthening mechanism. Pinning of grains boundaries by GNPs led to uniform grain size distribution in the composites structure. Overall, graphene reinforcement has offered 86% improvement in specific strength of aluminum matrix.

Research on graphene/nanostructure hybrid materials has been gaining momentum in recent years, with wide-ranging applications in gas sensing and detection. Specifically, noble metal decorated graphene-based novel structures were found to be extremely sensitive and selective owing to the synergistic effect of the compound configuration. In this article, recent developments in graphene/noble metal nanostructure hybrids and their promising potential in gas sensing applications has been highlighted. More significantly, an understanding of the electronic mechanism of gas sensing is presented with a specific emphasis on electron transfer and junctions effects at the graphene/nanostructure interfaces. Finally, the future research prospects of application of bi-metallic and tri-metallic nanostructure/graphene-based hybrids and the challenges in this new and rapidly growing domain are discussed.

Here we report application of commercially available soda lime glass as transparent, conducting electrodes. Transparent glass substrate, without any surface preparation, was coated with reduced graphene oxide (rGO), through a simple, scalable, easy-to-operate and low-cost deposition technique to render conductivity to it. The process involved dip coating of graphene oxide (GO) solution on soda lime glass, followed by reduction of GO to rGO by thermal annealing process at 500 °C in Ar or Ar + H2 atmosphere. Though there was no significant effect of atmosphere (Ar or Ar + H2 gases) on the transmittance of the electrode, lower sheet resistance was observed in the films reduced under Ar + H2 cover, as compared to those reduced in only Ar atmosphere. The highest transmittance of 97.98% and lowest sheet resistance of 12.55 × 103 Ω/sq was achieved under different processing conditions. De-bonding energy of GO and rGO (Ar and Ar + H2 treated) with the soda lime glass was also quantified using nanoscratch technique to throw light on the adhesion behavior of the film with the substrate.

This article shows the efficacy of transition metal (Ni) as a top layer on glass in the formation of graphene domain. Graphene films were grown on glass substrates from highly ordered pyrolytic graphite by pulsed laser deposition (PLD), with the help of 250 nm thick Ni thin film. The as-synthesized graphene films were characterized by UV–Vis spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and Optical microscopy. The Raman spectroscopic measurement reveals that catalytic film of Ni enhanced the characteristic 2D-peak of graphene on glass substrate, indicating formation of graphene domain; while similar peaks were not detected in the absence of Ni. Moreover, Raman spectrum has shown less structural disorder in the resulting graphene film with the presence of Ni surfactant. The surface morphology of the as-synthesized graphene film was studied by scanning electron microscopy and optical microscopy. The present study shows an effective and exciting route to obtain high-quality graphene on glass substrates using PLD. Keywords: Graphene, PLD, Raman spectroscopy, UV–visible spectroscopy, SEM, XPS

Carbon nanotubes (CNTs) were directly grown on copper and nickel foams by chemical vapor deposition (CVD) process, followed by the deposition of reduced graphene oxide (rGO) through dip-coating method. These three-dimensional hybrid structures were used as cold cathodes to perform field emission tests under DC bias application. Field emission response of CNTs grown on metallic foams was compared with rGO coated CNTs samples. Field emission results demonstrate that the emission current density and field enhancement factors were significantly enhanced after rGO deposition on CNTs due to the formation of sharp protrusions in rGO sheets. Local field enhancement at the apex of sharp protrusions allows tunneling and hence emission of electrons from tips at considerable lower voltage. rGO coated CNTs based field emitters on nickel foam, among all studied emitters, demonstrated the highest emission current density of 64 mA/cm2, lowest turn-on field of 0.71 and the highest field enhancement factor of 15,999. Excellent field emission characteristics of metal foam based three-dimensional field emitters suggest the potential of the synthesized cathodes in various field-emission applications.

Advent of nanotechnology has generated huge interest in application of carbon-based nanomaterials as a possible replacement for conventionally used graphite as anode of Li-ion batteries. Future Li-ion batteries demand high capacity, energy, power, and better safety, while graphite falls short of fulfilling all these necessities. Inspired by high conductivity, flexibility, surface area, and Li-ion insertion ability, a number of nano carbon materials, individually or as a composite, have been studied in detail to identify the best suitable material for next-generation energy storage devices. Many of these nano-C-based structures hold good promise, although issues like density of nanomaterials and scalability are yet to be addressed with confidence. This article aims to summarize the major research directions of nano-C materials in anodic application of Li-ion batteries and proposes possible future research directions in this widely studied field.

Few layer graphene was deposited on p-type Si (I00) substrates by pulsed laser deposition of highly ordered pyrolytic graphite (HOPG) target at a relatively low temperature of 700 °C, without any catalytic layer. Effect of laser energy on the ability to produce the crystalline graphene was studied. It was observed that a laser energy of 220 mJ/pulse lead to form few layer graphene while higher laser energy of 440 mJ/pulse was detrimental to precipitation process. The reasons behind this observation are also discussed. Graphene samples were analyzed using Raman spectroscopy and surface morphology of graphene samples was confirmed using field emission scanning electron microscope (FE-SEM).

A wide variety of carbon nanostructures, from zero-dimensional fullerene through one-dimensional carbon nanotube to two-dimensional graphene, have attracted attention of scientific community worldwide for their exciting properties. Carbon-based nanomaterials have found applications in a vast field—electronics, sensors, biotechnology, energy, structural, etc. We have concentrated our effort in developing new engineering nanomaterials (graphene, carbon nanotubes) and their device applications in the field of energy generation and storage, nanoelectronics, and bio-electronic sensors. This article aims to capture those recent research efforts in synthesis and applications of carbonbased nanomaterials.

All-graphene based cathode and anode structures were fabricated and their application as a flexible and transparent field emission device is presented. The graphene film was grown on a Cu foil by thermal chemical vapor deposition and later transferred to a polymer substrate through a hot press lamination technique. Multiwall carbon nanotubes (MWCNTs) were spin-coated onto a graphene film on a transparent, flexible substrate to form the cathode of the field emission device. A green-phosphor coated graphene-PET film was used as the anode. The device showed good transparency and flexibility as well as giving an appreciable emission current. The simple processing techniques used can easily be upgraded to a larger scale and be tailored for any transparent and flexible substrate. The device offers exciting applications of carbon nanostructures in foldable electronics.

Graphene, one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, has grabbed appreciable attention due to its exceptional electronic and optoelectronic properties. The reported properties and applications of this two-dimensional form of carbon structure have opened up new opportunities for the future devices and systems. Although graphene is known as one of the best electronic materials, synthesizing single sheet of graphene has been less explored. This review article aims to present an overview of the advancement of research in graphene, in the area of synthesis, properties and applications, such as field emission, sensors, electronics, and energy. Wherever applicable, the limitations of present knowledgebase and future research directions have also been highlighted.

Graphene was grown directly on porous nickel films, followed by the growth of controlled lengths of vertical carbon nanotube (CNT) forests that seamlessly emanate from the graphene surface. The metal–graphene–CNT structure is used to directly fabricate field-emitter devices and double-layer capacitors. The three-dimensional nanostructured hybrid materials, with better interfacial contacts and volume utilization, can stimulate the development of several energy-efficient technologies.

This paper presents our recent results on carbon nanomaterials for applications in energy storage and bio-sensor. More specifically: (i) A novel binder-free carbon nanotubes (CNTs) structure as anode in Li-ion batteries. The interfacecontrolled CNT structure, synthesized through a two-step chemical vapor deposition (CVD) and directly grown on copper current collector, showed very high specific capacity - almost three times as that of graphite, excellent rate capability. (ii) A large scale graphene film was grown on Cu foil by thermal chemical vapor deposition and transferred to various substrates including PET, glass and silicon by using hot press lamination and etching process. The graphene/PET film shows high quality, flexible transparent conductive structure with unique electrical-mechanical properties; ~88.80 % light transmittance and ~ 100 Ω/sq sheet resistance. We demonstrate application of graphene/PET film as flexible and transparent electrode for field emission displays. (iii) Application of individual carbon nanotube as nanoelectrode for high sensitivity electrochemical sensor and device miniaturization. An individual CNT is split into a pair of nanoelectrodes with a gap between them. Single molecular-level detection of DNA hybridization was studied. Hybridization of the probe with its complementary strand results in an appreciable change in the electrical output signal.

Large scale fabrication of graphene over transparent flexible polymer, Polyethelyne tetrapthalate (PET), and its application in flexible field emission display is reported here. We used Cu foil (~160 mm x 60 mm) to grow graphene by thermal chemical vapor deposition process and transfer the graphene over a polymer using a straightforward hot press lamination technique. The fabrication method is facile as there is no rigorous chemical process involved and the process is also applicable towards the fabrication of large scale graphene over a wide range of transparent flexible substrates for foldable micro-electronics applications. Further, we demonstrate the application of graphene/PET polymer film as anode of transparent flexible field emission display device. The device shows low turn-on voltage ~ 1.75V/μm and high current density of ~ 65μA/cm2 with field enhancement factor (β) ~1000.

We present the fabrication and electrical characterization of large graphene structure on polyethylene terephthalate (PET) flexible substrate. Graphene film was grown on Cu foil by thermal chemical vapor deposition and transferred to PET by using hot press lamination. The graphene/PET film shows high quality, flexible transparent conductive structure with unique electrical-mechanical properties; ∼88.80% light transmittance and ∼1.1742 kΩ/sq sheet resistance. We demonstrate application of graphene/PET film as flexible and transparent electrode for field emission displays. Our proposed techniques can be tailored for any flexible substrate and large scale production, which could open up exciting device applications in foldable electronics.